Muffler with loop-shaped band movable by gas pulsations



June 6, 1967 s. o. THRASHER MUFFLER WITH LOOP-SHAPED BAND MOVABLE BY GAS PULSATIONS Filed Dec. 2, 1965 35 INVENTOR.

5H4A/A/0/V0. Kansas/2 BYW #0 3 0 -QQ mm? I United States Patent Calif.

Filed Dec. 2, 19 65, Ser. No. 511,193 7 Claims. (Cl. ISL-S8) The present invention relates to mufflers, and more specifically to a novel mufller construction which is particularly adapted to use with twocycle internal combustion engines.

Engines employed to drive lawn mowers, chain saws, motorized racercars and similar machines are usually of a low horsepower, two-cycle internal combustion type. Although such engines are relatively inexpensive and have a low fuel consumption, they are extremely noisy in their operation.

It is well known that one of the primary sources of twocycle engine noise is exhaust leaving the engine and repeatedly striking the atmosphere in compact volumes. To deaden or otherwise absorb such explosive sounds, it is, of course, desirable to include some sort of muffler on the exhaust manifold of the engine. Unfortunately however, commercially available mufflers develop relatively large back pressures which cannot be tolerated by low power two-cycle engines. Also, conventional mufflers usually include a relatively long straight housing which is too large to be conveniently mounted on lawn mowers, chain saws and other similar machines employing twocycle engines. Primarily for these reasons, such twocycle engines usually do not include a muffler.

In View of the foregoing, it is an object of the present invention to provide a novel muffler construction which develops very low back pressures and is therefore ideally suited to use with low power, two-cycle, internal combustion engines.

Another object of the present invention is to provide a mufiier construction of the foregoing character which is extremely compact, lightweight, and readily attachable to the exhaust manifold of two-cycle engines commonly employed to drive lawn mowers, chain saws, motorized racer cars and similar machines.

A further object of the present invention is to provide a mufiler construction which not only develops a minimum back pressure but is also highly effective in its muflling operation.

Still another object of this invention is to provide a novel muffler for two-cycle engines which is inexpensive to manufacture.

Still another object of this invention is to provide a mufiier which is easily assembled and disassembled for servicing and replacement of parts.

The foregoing as well as other objects and advantages of the present invention may be more clearly understood by reference to the following detailed description when taken with the drawing which, by way of example, illustrates one form of mufiler construction embodying the features of the invention.

In the drawing:

FIGURE 1 is a perspective view of one form of mufller of the present invention in combination with and connected to the exhaust port of a two-cycle internal combustion engine;

FIGURE 2 is a perspective view of the separate component parts of the mulfier of FIGURE 1 including a cylindrical metal housing, a loop-shaped band having a multiplicity of openings therein, and a cap having a plurality of apertures therein, and illustrates the manner of con- 3,323,614 Ce Patented June 6, 1967 struction of the component parts and their mode of combination to form the mufller;

FIGURE 3 is a sectional side view of the mufller illustrating the mode of operation of the muffler; and

FIGURE 4 is a fragmentary sectional view of the mufller taken along the line 44 in FIGURE 3.

In the drawing, the muffler is represented generally by the numeral 10' and is shown in FIGURE 1 in combination with a small, two-cycle engine 12. The mufiler includes a relatively flat, generally, cylindrical metal housing 14 defining a cylindrical inner chamber 16 having a side exhaust intake 18 extending tangentially from the housing for connection to the exhaust manifold of the engine12. The housing 14 also includes an open end 20 and a closed end 22. The open end 20 is covered by a generally flat cover plate or cap 24 having a flanged marginal edge 26 for fitting over the outside of the housing around the open end thereof. The cap 24 is releasably secure to the housing 14 by a bolt 28 which extends from the center of the closed end 22 and passes through a central hole 30 in the cap to receive a nut 32 for locking the muffler 10 together.

The cap 24 includes a plurality of apertures 34 spaced from each other and arranged in a radial pattern around the central hole 30. The apertures 34 provide an exit to atmosphere for exhaust gases traveling through the muffler and preferably have a total open area greater than the cross-sectional area of the exhaust intake 18.

In addition, the cap 24 and closed end 22 of the housing include axially aligned holes or outward depressions 36 and 38. The depressions are spaced slightly from the inner wall of the housing 14 substantially midway between parallel planes including the exhaust gas intake 18 and the bolt 28 and provide means for pivotally supporting a loop-shaped metal band 40 between the cap 24 and closed end 22 of the housing and around the apertures 34 to isolate the apertures from the exhaust intake.

More particularly, the metal band 40 is an annular band having a multiplicity of openings 42 therein. A thin, pencil-shaped rod member .44 extends axially along the outside of a band and is secured thereto, as by welding.

1 Ear-shaped ends 46 and 48 ofthe' rod 44 extend into the depressions 36 and 38 and support the band 40 for swinging movement in the plane of the inner chamber 16 in re sponse to exhaust gas pulses received from the engine through the exhaust intake 18.

In particular, an exhaust gas pulse traveling down the exhaust intake 18 tangentially enters the cylindrical housing 14 and taking the path of least resistance, travels along the curved inner face 15 of the housing. Almost immediately, the exhaust pulse encounters the band 40 and exerts inward forces thereon which swing the band about the rod 44 away from the intake port. In moving away from the intake port 18, the band 40 absorbs some energy from the exhaust gas pulse.

As the exhaust pulse continues to travel along the curved inner face 15 of the housing 14, it loses further amounts of energy and also creates a slight vacuum or negative pressure on the curved outer face of the band 40 adjacent the intake 18. The negative pressure, together with the force exerted by the exhaust pulse on the side of the band 40 opposite the intake 18, causes the band to swing back toward the exhaust intake, absorbing additional energy from the exhaust pulse.

Traveling further around the curved inner face 15 of the housing, the exhaust pulse loses still additional amounts of energy and develops a vacuum or suction force on the curved outer face of the band 40 remote from the exhaust intake 18 which together with the positive pressure of the exhaust pulse on the intake side of the band causes the band to swing back away from the J exhaust intake. As this occurs, still further energy is ab sorbed from the exhaust gas pulse.

The swinging operation of the band 40 is repeated again and again as the exhaust gas pulse circulates around the inner face 15 of the housing 14. As this occurs, energy is continuously absorbed from the exhaust gas pulse and the pulse is broken up, smoothed out, and eventually, after losing sufficient momentum, passed through the openings 42 in the band 40 and outwardly to atmosphere through the apertures 34 in the cap 24.

The same result occurs for each exhaust gas pulse received by the muffler such that exhaust gases flow smoothly from the mufiier to atmosphere. Since all concentrated volumes have been removed from the exhaust, explosive forces and sounds are not created upon the exhaust gases reaching the atmosphere and exhaust gas noises are substantially eliminated.

In addition, as the exhaust gas pulses travel around the curved inner face of the housing 14 past the exhaust intake 18, vacuum or suction pressures are developed across the intake which effectively draw or pump exhaust from the engine. This has the dual effect of aiding in the production of a minimum back pressure within the muffier 10 and of increasing the power and operating efiiciency of the two-cycle engine 12 connected to the muffler.

Acccordingly, the muffler 10 is ideally suited to use with low power, two-cycle engines such as employed in lawn mowers, chain saws, racer carts and similar machines. Moreover, the foregoing advantages are achieved in a highly compact, simple design which is inexpensive and easy to manufacture. Further, the muffler 10 is very easy to assemble simply by dropping the band 40 into place with housing 14 and by covering the open end of the housing with the cap 24. Should the muffler 10 require servicing, the assembly operation is simply reversed with the cap 24 being removed to expose the band 40 which may be readily replaced or cleaned as desired.

While in the foregoing, a particular form of muffler has been described in some detail, changes and modifications may be made in the illustrated form without departing from the spirit of this invention. It is therefore intended that the present invention be limited in scope only by the terms of the following claims.

I claim:

1. A muffler comprising: i

a hollow housing including an inner chamber having an exhaust intake port and an outlet port;

a loop-shaped band stationed within said chamber around said outlet port to impede the flow of gases from said intake port to said outlet port;

and means supporting said band for movement within said chamber in response to exhaust gas pulses entering said chamber through said intake port to thereby absorb energy from said pulses as they travel along the inner surface of said chamber around said band past the intake port and hence to and through said outlet port.

2. The mufiler of claim 1 wherein said means supporting said band includes pivot means supporting said band for swinging movement within said chamber.

3. The mufller of claim 2 wherein said band includes a multiplicity of apertures.

4. The muffler of claim 3, wherein:

said chamber is generally cylindrical in shape;

said intake port is a side port;

said outlet port is an end port;

and said band is an annular band.

5. The mufl'ler of claim 4, wherein said pivot means includes axially extending means contacting opposite ends of said chamber to support said band for swinging in the plane of said chamber.

6. The muifler of claim 5, wherein said housing is a cylindrical housing and wherein said muffler includes a removable cap for covering one end of said housing and chamber.

7. The muffler of claim 6, wherein said means for pivotally supporting said band includes aligned holes in said cap and in an opposite end of said housing and ears extending outwardly from said band into said holes.

References Cited UNITED STATES PATENTS 3,074,506 1/1963 Benes 18l40 FOREIGN PATENTS 655,022 1/1938 Germany.

RICHARD B. WILKINSON, Primary Examiner.

R. S. WARD, Assistant Examiner. 

1. A MUFFLER COMPRISING: A HOLLOW HOUSING INCLUDING AN INNER CHAMBER HAVING AN EXHAUST INTAKE PORT AND AN OUTLET PORT; A LOOP-SHAPED BAND STATIONED WITHIN SAID CHAMBER AROUND SAID OUTLET PORT TO IMPEDE THE FLOW OF GASES FROM SAID INTAKE PORT TO SAID OUTLET PORT; AND MEANS SUPPORTING SAID BAND FOR MOVEMENT WITHIN SAID CHAMBER IN RESPONSE TO EXHAUST GAS PULSES ENTERING SAID CHAMBER THROUGH SAID INTAKE PORT TO THEREBY ABSORB ENERGY FROM SAID PULSES AS THEY TRAVEL ALONG THE INNER SURFACE OF SAID CHAMBER AROUND SAID BAND PAST THE INTAKE PORT AND HENCE TO AND THROUGH SAID OUTLET PORT. 